First let’s define tartrates. You may have heard them called “wine diamonds.” You can find them on your cork, in the neck of the bottle, and in extreme cases floating in the wine itself (or sunk to the bottom). It’s not bad. It’s just not pretty. Some consumers think it’s a “fault.” It’s not. But to prevent any misconceptions or unhappy conversations, many winemakers will stabilize against them.

What these crystals actually are are deposits of potassium and calcium tartrates. It often happens when a wine (that hasn’t been stabilized against tartrates) sees a dip in temperature—tartrates are less soluble at cold temperatures.

How to Stabilize Against Tartrates:

Cold stabilization: wine is held at a cool temperature (around 25°F) for (approximately) 8 days in order to form tartrate crystals which can then be filtered out before bottling. NOTE: Colloids must be removed via fining before undergoing this process. ANOTHER NOTE: This process removes the “more common” potassium bitartratenot calcium tartrate

Contact process: potassium tartrate is added to the wine and speeds up the start of the crystallization process; wine is cooled to about 32°F and crystals can be filtered out after one or two hours.

Electrodialysis: a charged membrane removes selected ions; can remove both potassium and calcium ions (and, to a lesser extent, tartrate ions).

Ion exchange: replaces potassium and calcium ions with hydrogen and sodium ions, which will not drop out of solution.

Carboxymethylcellulose (CMC): cellulose is extracted from wood and prevents tartrates from developing to a visible size; popular method in the production of inexpensive white wines, but not suitable for red wines, as tannins will render the CMC ineffective and, thus, causes a haze. NOTE: “CMC keeps wine stable for a few years.”

Metatartaric acid: this is a compound that can be added that prevents the growth of both potassium and calcium tartrates into a visible size; the compound is unstable and will lose its effect over time (especially if stored at warmer temperatures between 77 and 86°F); is used more for red wines (CMC is more effective for white and rosé wines).


How’d I do? Did that all make sense? Anything I forgot or you want to add?

Thanks again for studying with me!

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